KABUL — In a rupture that could send seismic cracks through Afghanistan's shaky political landscape, one of the country's most powerful leaders has definitively broken with President Ashraf Ghani after months of alternating between private negotiations and public denunciations of his government.

Atta Mohammad Noor, 53, the last remaining Afghan regional strongman and the wealthy governor of northern Balkh province for the past 16 years, has either resigned or been fired, according to various statements and interpretations that circulated Monday in the capital.

The president's office said Atta had "offered his resignation" at some point in the past and had been replaced, but associates of Atta, a leader of the influential Jamiat-i-Islami party, said that the offer had been made "conditionally" during talks last year and that because his demands were not met, his dismissal would not be accepted.

Atta made no public comment Monday, but Foreign Minister Salahuddin Rabbani, the head of Jamiat, issued a statement calling Ghani's replacement of Atta a "hasty, irresponsible act against the stability and security of Afghanistan."

Rabbani said removing Atta was "in conflict with the principles" of a U.S.-brokered deal in 2014, after fraud-plagued and inconclusive elections, under which Ghani and his top rival, Abdullah Abdullah, agreed to form a temporary joint government. Abdullah, whose relationship with Ghani has often been tense, is also from the Jamiat party.

Atta, who is enormously wealthy, bankrolled Abdullah's presidential run. Atta also controls large numbers of armed loyalists, and after the 2014 election he threatened to overrun the capital with protesters if Abdullah were not declared the winner.

Now, Atta's sudden departure from office could force Abdullah to choose sides, potentially breaking up the already fragile national unity government.The government is backed by the United States and other Western countries, and the Trump administration is in the process of adding several thousand U.S. troops to help train Afghan forces in their fight against insurgents.

Some Jamiat figures said the party would completely "boycott" the Ghani government if Noor were not reinstated. The party is dominated by ethnic Tajiks, and it has long accused Ghani, an ethnic Pashtun, of ethnic bias. Atta had long demanded that Ghani give Jamiat more say in appointments and other perks, and he had reportedly agreed to resign as governor only if those demands were met.

Last summer, Atta publicly joined forces with another northern strongman and disgruntled government official, Vice President Abdurrashid Dostum, who had left the country after being accused of rape and assault by a political rival. Atta visited Dostum at his home in Turkey with several other political figures, and the group announced an opposition alliance called the Coalition for the Salvation of Afghanistan.

More recently, Atta accused Ghani's government of barring his plane from traveling to Kandahar, where a group of opposition figures and lawmakers, including Dostum, gathered to discuss problems with the Ghani government, including alleged meddling in parliamentary elections scheduled for July.

Atta is often described as having built an empire in Balkh province, using its border-customs revenue to build its capital, Mazar-e Sharif, into a model of development. He is known for ruthless behavior, including ordering the seizure and beating of a local official who threatened to expose corruption in the region.

News of Atta's removal came on a day when gunmen and a car bomber invaded a construction site near a national intelligence police training facility in the capital, underscoring the government's vulnerability on another front. The assault, claimed by the Islamic State, led to a six-hour gun battle in which all three attackers were killed. Some security forces were injured.